I shoulda knew better from the first few letters you sent me
The first two letters, you were tellin' me shit like
You respect me, like any other regular MC

from Eminem – Canibitch Lyrics on Rap Genius

Meaning

Canibus sent Eminem admiring letters, just like most Emcees who respect his work.
However, Canibus got a little crazy after the first few letters, as shown in the next few lines.

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